It is well known that cardiac arrhythmias, such as atrial or ventricular fibrillation, can be overcome by applying electrical energy to the arrhythmic myocardium. This procedure, commonly referred to as defibrillation or cardioversion, can be accomplished by applying the electrical energy either to the chest of the patient by means of conductive-metal paddles held in place by medical personnel or, during the course of cardiac surgery, by holding conductive-metal paddles in direct contact with the surface of the heart. Such procedures are well known and have been found to be generally effective in practice.
In addition, automatic defibrillation/cardioversion has been achieved by implanting an automatic defibrillating/ cardioverting device capable of detecting one of the aforementioned arrhythmias, and defibrillating/cardioverting the heart accordingly. Automatic defibrillating/cardioverting devices of this type have traditionally employed endocardial electrodes or epicardial electrodes, the latter of which is inserted in a rather invasive manner.
Additionally, another type of implantable electrode is a subcutaneous planar electrode, which does not violate the pleural cavity, and requires only minor surgery. A subcutaneous electrode is used in implantable cardioversion/defibrillation to discharge against one or more epicardial or endocardial electrodes. Subcutaneous electrodes heretofore known comprise a planar conductive screen. The implantation procedures for such subcutaneous electrodes require the formation of a subcutaneous pocket by blunt dissection, and the subsequent insertion of a suitable planar electrode. These planar subcutaneous electrodes result in discomfort in some patients, though they are used on a widespread basis in internal defibrillation/cardioversion.
The present invention relates to a tool and a method for implanting an array type or multi-segment subcutaneous electrode which is the subject of U.S. patent application Ser. No. 07/533,886, field Jun. 6, 1990. This type of subcutaneous electrode is as effective as planar electrodes and more comfortable than such planar electrodes. The present invention also relates to an improvement of the subcutaneous electrode disclosed in the aforementioned prior application.